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Why is the air inside airliners so dry (low humidity)?
The air inside an airliner is very dry which causes all sorts of passenger discomfort such as dry eyes, dry skin and in some cases headaches.
Why is the air so dry and what do or can modern designs do to improve the air humidty on board an airliner?

Maybe because it basically is ambient air (first heated up by the being squeezed into the engine and then again cooled down by the aircon packs) and ambient air at 30,000 ft tends to be dry. But I bet you're asking why the aircon packs don't humidify it any further.

Related: Can an airliner provide ground level cabin pressure, temperature, humidity etc?

Related: Why does cabin air have to be dehumidified?

Keep in mind you are also flying in a pressurized tin can miles high, and in minutes you reach air pressures appropriate to Colorado ski resorts, but without days to acclimate.  These factors also attribute to the discomfort.

Airborne diseases also spread further in dry air.

@Harper Except it's aluminium, not tin.

Given all the other discomforts of commercial air travel, I'd question whether low humidity is even noticable.  Also, I'd ask whether it is actually all that dry, given that you're sharing that aluminum can with a hundred or more other people, all of whom are exhaling & perspiring moisture into the air.

Those new really big airliners, the Dreamliner, don't have this problem.  They're great.

@Cloud tin cans are also not made of tin, but people call them that anyway.

@Fattie Not for the environment though :|

What happens during a flight cycle is the humidity is high during departure, from ambient air and the moisture from the pax, but over time the air dries out because the bleed being supplied to keep the pressure hull "inflated" is coming from the engine compressors, which at 35000 ft has almost no humidity, and what humidity there is is being extracted by the Air Cycle Machines that condition the bleed (by heat exchanger condensate).
It's important to note the air cycle air conditioning process (787 excluded): Take hot high pressure bleed air, take away some of the heat with heat exchangers while keeping the pressure up, boost the pressure and temperature some more with an air cycle machine - more or less a turbocharger that feeds itself - , cool that off some more with more heat exchangers, then  finally allow the significantly cooled but still very high pressure air to expand and drop down to just above cabin pressure.  This process can take 500F air bleed from the engine compressor and chill it to -40 if you pass all of it through the air cycle machine (only some goes through, and gets mixed with bypassed bleed after, and the air cycle discharge itself is normally kept to not less than > freezing).  Anyway, this process takes whatever humidity there is and removes it, leaving bone dry air.  Moisture control is a big deal with Air Cycle Machines because condensate water that forms during the cooling process will rapidly erode the ACM turbine and ruin the ACM, so you have water separators that extract moisture that condenses from being chilled.
Then at altitude, there's almost no ambient moisture in the first place and you end up with really dry air from ambient being pumped in, how much depending on how leaky the pressure hull is (they can leak quite a lot) offset by humidity coming from all the pax.  At high altitudes after a period of time the dry incoming air wins out and the pax humidity isn't enough and everybody starts to dessicate, again, depending on how leaky the pressure hull is.  An older leaky airplane will get a lot drier inside than a newer relatively tight one.
As Mackk says, one of the big issues is that what moisture does get around the cabin ends up condensing on the inside of the pressure hull.  It slowly gets absorbed into the insulation.  Airliners that operate in humid environments down low will carry hundreds of pounds of water in the cabin insulation because of the condensation cycles from flights, and you will often see insulation set out to dry when airliners are in for heavy check inspections.  What water doesn't soak into the insulation collects at the bottom of the fuselage and promotes corrosion (one solution is to pump dry conditioned air directly into the space between the insulation and skin - so called "zonal dryer" systems).
Anyway, you can see there is a this-or-that problem.  Air moist enough to keep pax happy plays havoc with the interior. Air dry enough for a happy interior generates dry air complaints.  In general, the industry tends to go with the latter.

How did 787 manage it without the suite of problems for the operators?

I don't know much in the way of details of the 787, but it doesn't use engine bleed.  It uses an electric based refrigeration/heating system, has a much more air tight composite pressure hull, so that moisture level can be managed more precisely at a higher level as per Dave's answer.

The ACM extracts the water from the air? Where is that water kept? Is it leaking out of the aircrfat? I guess that there can be a significant volume of water, especially when an aircraft operates in tropical environments where the humidity of the air is a lot higher. As the door closes after boarding this humid air is captured inside the cabin.

It's either dumped overboard through a drain, or is commonly routed to an 'aspirator' that is used to spray the water on the heat exchangers to improve their efficiency.  It doesn't have to be tropical.  Look at an airliner on the ramp with packs on running off APU bleed on any humid summer day in NA, and you will sometimes spot a little drain hole with water spitting out of it.  There is often still condensate moisture even after leaving the packs, and so you will typically find a last gasp water separator in the air conditioning ducting going into the pressure hull.

I'm sure the packs create condensate on the ground, but how found it create any at altitude. The dewpoint at 35,000 feet is like -50° C. Where would condensate come from?

See para 3: "Then at altitude...."

Why is the air so dry

Its in part by design and in part a constraint of the system. All aircraft are at risk of corrosion not just big airliners. So keeping them dry is a good way to cut down on that risk. Even though they use fancy anti corrosive paints these days internal corrosion presents a serious risk as some areas may only be exposed during a maintenance check.
Big airliners simply pressurize the exterior air for the cabin so if the air outside is dry, which at 35,000 feet it is, then the air in the cabin is going to be dry as well.

and what do or can modern designs do to improve the air humidty on board an airliner?

Not much, the introduction of carbon composites to airframe design and construction has made corrosion less of an issue. In turn aircraft can tolerate a higher moisture content. This is effectively how the 787 was able to raise its moisture content to 14%. However the larger issue is where that actual moisture comes from, the air at high altitudes is not getting any more humid so the only way to increase the humidity is to either recycle the moisture you have or cary water and inject it. Both of these options present the same issue a heavy complex system and in aviation its all about weight. At 8.34LBS a gallon no one really wants to cart water around just to make the cabin a bit more comfortable, especially when that load can be used for revenue generating cargo or passengers.

200 humans exhaling persistently in an enclosed, relatively warm, high pressure atmosphere creates large quantities of condensation on the cold interior surfaces & structure of the aircraft hull, creating a serious corrosion liability. Like computer mainframe facilities being carefully air conditioned & temperature controlled, de-humidifying the air is done deliberately for the benefit of the equipment, not the human occupants. Modern aircraft such as the 787 can have (slightly) increased ambient cabin humidity because of improved condensation mitigation & corrosion resistance.

The humidity inside the plane has three constraints:

at what point does the humidity become a corrosion risk for the plane?  The 787 and presumably other future planes are now mostly "plastic" (composites) and can't corrode, so this limit is just in the process of increasing rapidly.
what the hardware can in theory deliver: air at altitude is cold, and warming it lowers the humidity a huge amount.  (This is why static electricity is a problem in the winter in cold climates.)
the increased cost of carrying around literally a ton of water is considered by the airline along with whether the increased comfort it provides will get customers to pay more or be more loyal.  In short, even if the plane can do it, the airline may decide not to.


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Why don't short runways use ramps for takeoff?
Say you had a runway for light aircraft, but only 700 meters or so of runway. Wouldn't it help to end the runway with a ramp that is ~40 meters above ground and slightly facing the sky at a gradient of 5%. Imagine the runway below was 700 meters long:

The point is to put the plane in a position where it is off the ground and in an upwards trajectory so it doesn't have to raise it's own pitch (but still travelling at near-takeoff speed), I think this could be useful with gliders (maybe with some sort of winch to launch it).
If money were no object, what would the flaws be in this sort of contraption? Is there a reason most runways are flat? Is this sort of thing used on any aircraft carriers or other remote-takeoff locations?

Because of relief, some altiport have convex runway.

If the plane does not have enough room to accelerate to speed, the plane would hit the end of the runway and immediately be in a stall condition.

V1.
There are other valid reasons, as have been listed - cost, bidirectional runway use, etc. These would still not completely disqualify ramps, just limit them to very special circumstances. But the one disqualifying factor is that a ski jump takeoff removes the necessary element of safety airliners depend on during takeoff.
Up to a certain airspeed, called V1, an aircraft on a sufficiently sized flat runway can decide to abort. Using all available means, mostly brakes, an aircraft can halt its takeoff run and stop by the end of the runway. With a ski jump takeoff, you don't get that luxury - go off the ramp too slow and you fall off the end, nose first into the ground.
This is not a concern for carrier takeoffs. Every takeoff or landing on a carrier is a close call as it is. There's no spare runway for second thoughts. If things go wrong enough, the pilot has to pull the eject handle before he plunges into the water. In that situation, a ramp adds safety, giving a few more seconds on that ballistic trajectory.
So ski jump ramps are used on carriers that don't have much more expensive and complicated catapults. They are extremely effective there; just a 3 meter tall ramp can cut the takeoff roll in half for a fighter. But this comes at the cost of committing to it completely, do or die (which is the case on carriers anyway).
Since there's no eject handle on airliners, every takeoff has to be a safe one. This means being able to abort the takeoff if you develop a problem on the runway, such as your engines not spinning up to takeoff thrust.
The only way you could get a safe enough V1 with a ski jump is by having a runway of normal length, and then some, before the ramp, which removes the whole point of installing a ramp. You'd never reach it except on aborted takeoffs.

This. In summary, if you haven't reached the conditions to safely sustain flight by the time you're at the end of the runway, the last thing you want is to be lofted into the air anyway.

^ If I've reached the end of runway and I'm not airborne and I'm still on my takeoff run, I'm dead.

I suppose you could build a runout past the jump, but it would defeat the "short runway" purpose.

Imagine what'd happen with this sort of configuration if you were stuck in a reject-at-rotation scenario due to say, an elevator jam or disconnect during takeoff...

I warmly agree with Therac's particularly clear (and exact IMO) explanations. I would add the example of the Harrier fighter, a rare example of really effective and useful STOL (most others are too costly, slow, or too light useful weight). Spectacularly effective with the ramp it most often uses on carriers or on ground.

@Jimmy - a good point, except that the end of a flat runway could be equipped with an overrun net to increase survivability.

To put it simpler: no need to "jump" from a ramp if you do not have the speed necessary to fly. No minimum speed no enough lift from wings no fly.

What happens at the end of ski jumps isn't flight. It's falling, with style.

Because then you can only land in one direction.
What do you do if the wind blows exactly along the runway so that departing and landing planes have only tailwind then?
You would waste a precious runway by having such a big obstacle on it.
Moreover, an upward ramp might not be what is needed. Look for example at Lukla (or, as ManuH mentions in the comments, more generally to altiports). Here the mountains force the runway to be used in only one direction, and it is slanted so that departing aircraft will roll downhill, accelerating more thanks to gravity, and arriving planes will have to go uphill, decelerating more for the same reason, and thus both need less runway.

This is the correct way to use a sloping runway. A departing airplane needs horizontal velocity, not vertical velocity.

This is a smart but unfortunately not very good idea.
It seems quite reasonable to use a ramp at the end of a runway to help launch a plane into the air, and matches everyday experience when we are doing things with say skateboards or kites: an upward kick or movement is what they need to get them aloft.
The other answers have mentioned various reasons why this idea isn't going to work well, but there are two that I don't think I have seen.
Energy has to come from somewhere
Your ramp lifts the plane into the air, which means increasing its potential energy (height). However, that energy isn't free, and it has to come from somewhere. That somewhere is velocity: at the same time your ramp sends the plane into the sky, it reduces its forward speed.
The plane's wing needs that speed to get into the air; if it needed less speed in the first place, it would be flying by that point anyway. Your plane might be in the air, but it will have lost crucial speed and will most likely fall out of the air as a result.
It's a good thing to stay on the ground until you can fly
Your proposal aims to help the plane get into the air, sooner than it would otherwise. However, the reason a plane that's taking off is not yet flying is that it can't yet fly (or fly safely, anyway).
You cannot fly at "near-take-off speed"; gravity will claim you. You have to be at actual take-off speed.
If it's not able to fly, without help, the last thing it needs is to be in the air.

Energy has to come from somewhere, true. But it can be utilized better or worse. If you're hard-limited to only having X feet of runway (where X is just enough to take off), and at the end of it is certain death (cliff, concrete wall, sea), a ramp is better than no ramp. The problem is that it's still not safe enough. So in practice you'll have Y (Y>X) feet of runway instead, where a ramp isn't needed, and then there's no reason to have one, because the only way you're reaching it is in an aborted takeoff or landing overrun.

The energy argument isn't completely sound. Energy is not actually conserved in a plane takeoff: in particular at the moment of liftoff, the high angle of attack causes lots of drag losses. Basically, it's a quite inefficient conversion of forward- into upward-kinetic energy, whereas for a ramp that's pretty efficient (close to 100% if you can lock out the suspension dampers). So, the ramp would allow more of the engines' thrust to actually be converted into the kind of energy you need, and less of it into useless air turbulence.

Even at rotation, you might have sufficient airspeed to fly, but you might not have airspeed to climb well. I don't know about large aircraft, but that's certainly the case in the little one I fly, where rotation (as per the checklist) begins around 50 km/h IAS (rotation speed target is 70 km/h IAS, which is like one or two seconds later...) but best climb is about 100 km/h IAS. With full flaps (which is more than the normal takeoff flaps setting) and a light load, I believe it's possible to maintain forward flight in that one around 50 km/h IAS, but you'll be right at the edge of a stall.

If all of this answer was true, why are ski-jumps so useful on aircraft carriers?

@MikeBrockington It's a good point, but the circumstances of aircraft that take off from aircraft carriers (and the passengers they carry) are very different from those that use civilian runways. Just for example, occasionally an aircraft carrier launch will go wrong; navies are prepared to accept the implications of that in ways in civil aviation is not. The constrains of physics don't change, but priorities and acceptable risks do.

Re, "Energy has to come from somewhere." My first thought when I saw the question was, "wouldn't it work better to have the plane roll down the ramp at the start of takeoff?" That way, the energy that was used to lift the plane to the top of the ramp could quickly be converted to kinetic...

@MikeBrockington, Re, "why are ski-jumps useful..." Here's a guess: A pilot taking off from a flat runway must "rotate" the aircraft into the proper attitude for the climbout by pulling back on the yoke. I'm not an aeronautical engineer, but I can imagine a certain amount of aerodynamic drag/momentum lost associated with that maneuver. A "ski-jump" puts the aircraft into the same attitude without any aerodynamic interaction. Maybe that is more efficient.

Why does the "drop it in the air, THEN make it generate thrust so it stays in the air" method work for eg a missile but not an airplane?

@rackandboneman If an aeroplane has enough forward speed relative to the air around it, it will fly. If it does not, it will not fly. If it's on the ground and doesn't have enough airspeed, it will stay there. If it's in the air, it will fall out of it.

Nice question. Here are a few reasons and explanations.

As mentioned, it would only allow for take-offs in one direction, and if you put slopes on both ends, it would use up a lot of runway, because landing aircraft would have to overfly the vertical cliff of the ramp on the approach ends. Very dangerous.
One of the purposes of these ramps on aircraft carriers is to prevent launching the aircraft directly into the water. Aircraft carriers pitch up and down especially in rough seas. When an aircraft is being launched it takes a couple seconds and it may not be possible to pefectly time it so that the bow (front) of the ship is pointing up to the sky. If the seas are rough (as anyone with sailing experience can attest) there are moments where the bow is pointing at the surface of the ocean, even if its for just a few seconds, if that is the point when the aircraft is launched it could impact the water. So a slope helps in that scenario. Larger aircraft carriers that are more stable, and have a higher deck above water level can get away without a slope.
Aircraft carriers are not just floating runways, they are catapults! So, aircraft are pushed up the slope and launched into the air. Putting a slope on a runway, means that the aircraft's engine has to use up even more power climbing the uphill slope, which may likely slow it down even more, and the increased pitched means its pitching up and possibly slowing down which is a recipe for a stall. What a small aircraft on a very short runway needs is more speed not more pitch. Because we don't have catapults, a ramp is like taking off up hill, which will eat up some of our airspeed when the aircraft climbs the ramp. If the aircraft has a surplus of speed such that it would be above stall speed by the time it finished climbing the ramp, then it would work, but in that case, the aircraft had surplus speed, and could have just taken off normally before getting to the ramp.

Hope this helps.

One other consideration: this paper contains experimental results on the use of ramps, and one thing it makes clear is that the length of the run-up to the ramp, for any given airplane, is highly dependent on the gross weight. In a conventional take-off, you can start at the beginning of the runway and rotate when ready, but with a ramp, you have to start at pretty much exactly the right distance from it, which is a function of weight (and also wind speed, and you don't have the guaranteed ~30 kt baseline headwind of an aircraft carrier.) Any miscalculation or malfunction, and you are heading for a crash, especially as, as @Daniele Procida points out, the purpose of the ramp is to get you airborne before you are going fast enough to fly.
Note that starting your run long is not really a viable option (as well as at least partially invalidating the reason for using a ramp), unless you carefully control the speed at which you run onto the ramp. In the studies, the undercarriage loads went up to 90% of the maximum allowed (which also suggests that a ramp takeoff feels like a hard landing.)
This may be moot however: as @jamesqf points out, the question concerns light aircraft specifically. This study did not use any light aircraft, but it did show that ramps were more effective for aircraft with higher thrust-to-weight ratios, giving some quantitative evidence for the proposition that ramps would be of little use to light, low-powered aircraft. This seems quite plausible: a low-powered airplane would have to leave the ramp near to its out-of-ground-effect flying speed in order to continue flying, as a) on account of of its low power, it does not accelerate rapidly, and b) because this is happening at a low speed, the jump off the ramp does not give it much time to reach flying speed.
So using a ramp for light aircraft would be risky in several ways, require a greater level of skills than a typical light-aircraft pilot has trained for, and would be of little benefit anyway.

A ramp can help you leverage height and so can lead to increased efficiency so long as you don't miscalculate your lift during takeoff and your landing pattern is amenable to the airstrip's geometry, but this comes at a significant cost of lost safety. This is for the same reasons that early flight experiments involving cliffs or jumps or embankments were also a bad idea.
While a ramp does indeed transform some of your forward motion into altitude, altitude is not the same thing as lift. A machine that is not ready to fly from an elevation of zero feet is also not ready to fly from an elevation of 100 feet; the increased elevation instead can be converted into potentially lethal potential energy if the machine does not generate sufficient lift after it has been jettisoned.
The case of aircraft carriers using ramps as in @ymb1's answer is an interesting case of economy. There is often not a safe way to stall or maneuver out of a failed takeoff from an aircraft carrier owing to the shortness of the airstrip, so it is make or break.
A longer, flat runway is much better for most flights for safety reasons because you are not forced to rely on the aircraft's lift until after it has already proven itself sufficient for flight. A premature lift-and-stall or bouncing could also turn the ramp unintentionally into a very dangerous obstacle.

One reason would be the simple cost of such a ramp.  Either you have to build a structure (and maintain it), or you have to move a lot of dirt and compact it - and then keep it from washing away in the rain.
That said, I have flown at more than one airport where the shape of the land dictates something like a ramp.  (The Spanish Springs airport springs to mind, but there are others.)  You don't really gain much, since *(unless you're some kind of daredevil) you need extra runway for landing & possible go-arounds.
If you happen to be flying a hang glider, however, you can take this ramp launch thing to a logical extreme, and launch from Glacier Point in Yosemite: https://www.yosemitehg.org/
PS: On re-reading the question, I see that I completely misunderstood the OP's idea.  I assumed a launch from the top of the ramp going down, but the OP wants the plane to climb the ramp.  With that design, and barring REALLY powerful engines, the plane just gets to the top and falls off the other side.

Whatever the engine power, you are ignoring the fact that while on a runway the angle of attack of the aircraft is fixed until rotation, but when it is airborne it is not. Ignoring safety margins for simplicity, a plane can fly straight and level at 1 knot above its stall speed, but it can't take off at the same low speed because the AOA is smaller.

I disagree.  If an airplane can fly straight and level at one knot above stall it will be able to get airborne because of ground effect.  Once out of ground effect it just won't be able to sustain a climb.  This fact gets people in trouble...

Now that Yosemite launch looks like fun!  Yet another reason to work towards an H4.

@Michael Hall: Yes, and I have actually done this.  If you take off eastbound on the main runway of Stead airport (near Reno), the ground drops sharply to a (usually dry) lake a couple of hundred feet below.  Doing a check ride in a tired old 150, on a hot day, with CFI who must have weighed upwards of 250 lbs (and I'm not exactly small).  Lifted off in ground effect, went over the end of the bluff, and had to dive to pick up speed...

Anything you might want to build at an airport costs money, yet airports have all kinds of infrastructure and building any of these things is a major civil engineering project. Cost alone isn't an argument: you have to compare cost versus benefit.

@David Richerby: Sure.  Large cost (unless your terrain is already shaped like that), zero or negative benefit, per the other answers.

From a purely physics/ballistic trajectory point of view, a ramp 40m tall with a 5% gradient will do very little to get you airborne. Suppose you leave the ramp at near-takeoff speed of 100km/h, at a 5% gradient. If you continue on a purely ballistic trajectory, you'll reach level flight only 4m after leaving the ramp. If you had just built the runway just 0.5% longer, you'd be in the same position, with the same pitch, at the same speed, only at 40m lower altitude than with the ramp. This ignores lift generated from the angle of attack, but also the energy needed to climb the ramp, but it illustrates the point.
Building a ramp is far more expensive, impractical, and user-unfriendly than just building a slightly longer runway - an extra 4m of pavement is far preferable to a 40m tall ramp.

It's actually very effective for a short runway as you find on carriers. A tiny ramp, just 3 meters tall, shortened the takeoff run of an F-18 by as much as 50%. DOD study. This works by using the kinetic energy in a far more efficient way - splitting it between potential energy, vertical and forward momentum, rather than just forward momentum. E=mv^2/2, so that forward momentum is more expensive than it is effective.

@Therac Good point, ramps are more practical with a steeper angle and a shorter runway. That study tests a 9 degree launch angle, which would give triple the horizontal ballistic distance from the OP's 2 degree angle, and that does become a significant proportion of the runway distance for a runway that's only ~30m long!

@Therac True, but let's not forget the F-18 has a thrust-to-weight ratio of almost 1; I suspect that makes the ramp a lot more reasonable than for an airliner with TTW around 0.2. Not to mention the effect on the passengers :)

@Luaan You are correct about ramps being more effective for high thrust/weight airplanes - some figures can be found here: https://apps.dtic.mil/dtic/tr/fulltext/u2/a237265.pdf

100km/h isn't anywhere near take-off speed except for very small aircraft. A typical commercial jet will take off at 2.5 times that, or even more. And what's the relevance of the ballistic trajectory? If ballistics were even close to being the relevant model, the plane wouldn't be able to get up the ramp in the first place.

@DavidRicherby 100km/h is a reasonable figure because the question is specifically about light aircraft. You are right that the ballistics calculation is off, primarily because the effective weight is not the gross weight, but the difference between that and the lift. I haven't done the math, but I would guess that, for low-powered aircraft, the thrust is a secondary factor, mostly balanced out by the drag.

@sdenham Thanks for the correction on the kind of aircraft -- I'd missed that in the question.

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Why don't airships / blimps use frontal stabilizers or thrusters?

Is there any reason why frontal stabilizers aren't used on blimps or airships to ease maneuverability in, e.g., gusty winds? Even the indoor blimps have a tail rotor, not the nose rotor for rapid yaw movements.
Also, is there any reason why the "pusher" motors are used instead of puller-ones in the front (with an exception for the Lockheed Martin P-791)?

Possible duplicate of Why are vertical stabilizers always at the rear of an airplane?

Well, I dare to say this isn't a duplicate post. I've carefully chosen the title to contain the word "use" rather than "rely-upon" or "replace". How about classical reasonably sized tail-stabilizers working together with tiny nose-stabilizers for improved agility?

@fooot The other question you linked to is about "aircraft" and the answers only cover fixed-wing aircraft. This one is specifically about airships.

The principles of stability are the same.

Hmm, so why are there no aircrafts with i.e. 3 symmetric tail surfaces spaced at 120deg?

It's called a Bonanza V-Tail

@rbp: No, that only has two tail surfaces.

It depends if you want stability or manuverability. see this video.

It also has to do with if you want to attempt to keep laminar flow over the nose of the airship...

Welcome to Aviation.SE! This is a nice video, but could you please explain the key points from the video in your answer. In case the link breaks or the video is deleted, the answer would become useless otherwise.

Frontal surfaces are not stabilizers, they are destabilizers.
Form the pilot's point of view in the forward control cabin, manoeuvering accurately around the mooring point is far easier if corrections make the tail move a little to one side or the other, rather than making the nose, complete with their vantage point and the mooring rope, swing sideways.
Engines at the front just mess up the airflow over the body of the airship, while much of their thrust is dissipated in the mess. At the back they can help re-energise the boundary layer. Propellers also add side area and have a secondary action to stabilize or destabilize in the same way as fixed surfaces.
However most airships are multi-engined, with them installed in pods along the sides. Historically these installations have varied with pushers, tractors or both installed on the one pod. More recently, swivelling ducted fans have become commonplace.

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What is this partially disassembled aircraft in the desert?
I found this plane on Google Earth. I'm guessing it is being deconstructed, as there are no factories nearby. What countries could it have originated from?

The coordinates are 35°54'10.9"N, 117°43'51.6"W. Here's the location on Google Maps.
The plane is about 41 feet long, and seems to have had a wingspan of about 30 feet.
Also, if it is possible, what kinds of planes could this be?
Sorry if this question is not really possible to answer. I'm a complete beginner at aircraft.

So, you found what looks like an F-8 missing a wing in the middle of the USN's Air Warfare Center at China Lake.
It resembles the F-8 a lot:

Image Source
As @Andrew said in a comment, the plane might be an F-11 which has a little closer resemblance to your picture.

Image Source

Thanks! I wonder what they are doing with an airplane that was decommissioned 16 years ago

@MCMastery Probably seems like they are bombing it or something like that since it is an "Air Warfare Center".

I don't know what plane it is, but I'm skeptical of it being an F-8. Look at the horizontal stabilizer. The F-8 has almost a delta wing for a stabilizer, while the one in the image is more of a swept wing. The wing tips also don't look quite right, and the positioning of the canopy seems further back than on the F-8.

@BretCopeland Hmm, then it could be an F-100. But there are some parts that don't fit...It does not look that much of an A-7.

Hmmm, I don't know. A little more plausible. It still doesn't look quite right to me, but at the same time, it's a really low resolution image of a damaged airplane, so it's hard to know what elements of the plane are real, and what are artifacts. For example, the two black dots on the fuselage above the wings, is that a real thing, or damage, or open panels, or artifacts?

@BretCopeland Looking at all the different images of planes, the F-8 seems the closest match.

I did a quick overlay of the F-8 with the image, and they just don't look like a match to me at all. Look at the sweep of the leading edge of both the wing and the horizontal stabilizer. They're simply not the same airplane. https://i.sstatic.net/MfJmM.png

There is always the possibility that google earth image is distorted.

It is definitely not an F-8. The F-8 has two wings.

F-11 not F-8? https://en.wikipedia.org/wiki/Grumman_F-11_Tiger#/media/File:Grumman_F11F-1_Tiger_drawings.png The fuselage seems to have the same shape, and the F-11 stabilisers look closer to what you have than those on the F-8.

Overlay of the F-11 with the image. It's a perfect match, so the plane is/was almost certainly an F-11.

Another reason it's not an F-8 is the fact that you can clearly see the air intake ducts on the sides of the fuselage. The F-8 has a single air intake under the nose.

Shape of the wing and stabilizers match F-11. (aka F11F) Layout of the fuselage: nose - cockpit - air intakes - tapering fuselage - wing - non tapering fuselage - horizontal stabilizers, match the F-11.
F-8 cockpit much further forward, has no lateral air intakes, horizontal stabilizer shape doesn't match. Gnat has a longer nose, no tapering fuselage ahead of the wing, too much taper on fuselage aft of wing. F-100 has no lateral air intakes.
What's it doing there? It's a simulated target. Photo, radar and electro-optical sensors, not to mention pilot eyes, can locate and identify it. The shipping containers look like shipping container or sand-bag revetments.

Thank you, this is a big reason I was asking the question - What is it doing there?

It could possibly be the Folland Gnat.

The profile looks more like the accepted answer.

This seems extremely unlikely. The US military never used the Gnat, and the Gnat is considerably smaller than the plane pictured (29 long and 22ft wingspan, vs approx 40ft and 30ft). The Gnat tapers much more at its tail, and the wing joins the fuselage right behind the cockpit, whereas the pictured plane doesn't taper much at the tail and the cockpit seems to be a long way forward of the leading edge of the wing.


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How is the marine perimeter of a coastal airport secured?
Nice Côte d’Azur Airport is bounded on three sides by the sea, which is infested with oligarchs screaming around in powerboats and industrialists on huge yachts, all in close proximity (meanwhile the airport is full of their private jets).
A lot of this and other incessant marine activity takes place within swimming distance of the edge of the airport itself. The airport looks remarkably vulnerable to someone who could in effect simply swim up to the edge of the runway.
How is the security of this apparently porous perimeter, and that at other airports in similar positions, maintained?

In the background (top) "La promenade des Anglais' beach, where a terrorist attack occurred in 2016. This is the west side of the runways, seen from river "le Var" (bottom of your image). You can see the fence (see link below). Still from time to time... there is an intrusion in the security perimeter.

The fence stops between runway ends and does not protect access from the waters: Geoportail aerial view.

Often time there will be a fence installed as is the case at Maho Beach where people line up at the fence to get up and close to takeoff. The fence appears to have what looks like barbed wire on top.
If there is not enough clearance markers in the water may denote an area for boats to stay out of. Such is the case in St Barts. Aside from creating something a prop can snag these provide little security.
Assuming its a controlled airfield there is a good chance the controller in the tower can physically see the coast (with binoculars). If you floated up in any boat of size there is a good change you would simply be seen.
If you are talking about the departure end of the runway, it can also be difficult to just walk up to the back of a spooled up jet.

You can add video surveillance, intrusion detection systems and patrols (specially in France were the so-called "Plan Vigipirate" and "Sentinelle" are active).

Often the intrusion detection systems are only installed around the aircraft parking areas to detect anyone attempting to approach and tamper with parked aircraft.  The taxiways and runways are left merely to surveillance. Or, they may have ground radar running during non-usage hours that can detect intruders approaching from the sea area, with thermal image cameras that can "see" intruders at night. The technology also exists to tie these together, so the radar can detect the intruder, tell the camera where to look, and notify security while also tracking the intruder.

I don't know the specifics for LFMN (Nice Côte d'Azur), but KBOS in Boston, Massachusetts, a major international airport which is even more surrounded by water than LFMN is and where the runways go right up to the shoreline, uses a set of buoys to demarcate a restricted security zone in the surrounding waters.
This zone is patrolled by state, local, and harbor police and the Coast Guard, and anyone who enters without authorization is subject to prosecution:

The Massachusetts Port Authority (Massport) began installing 29 buoys around the 6.6 mile perimeter of Logan International Airport today. The buoys clearly mark the 250-foot inner airport security zone and will serve as reminder [sic] to boaters to steer clear of the airfield. The security zone was established by the legislature at the request of the Authority in 2002 as part of the Chapter 90 General Laws Section 61 and is one of many security enhancements Massport has implemented at Logan.
[...]
The buoys extend approximately five feet above the water so they are clearly visible from a distance. The buoys are similar to the buoys that mark the main channel of Boston Harbor. Three types of marine buoys of different size will be installed along the 250-foot security zone demarcation line ---- Class III, Class IV and Class IV.
The security perimeter is patrolled by State Police, the Coast Guard, Boston Police, the Environmental Police and the Boston and Winthrop Harbormasters. Only authorized law enforcement and military vessels will be allowed in the inner security area. Boaters who enter the security area for non-emergency purposes will be subject to prosecution and State Police will keep a database of offenders. ["Massport Installs Buoys Around Logan Security Zone; Multi-Agency Enforcement Underway" (Massport press release); my emphasis.]

Fences don't prevent intrusions, guards do. A fence without guards won't resist scaling too long. Not even a high wall with barbed wire on top will. The fence mainly serves as a clear demarcation of the restricted area, and as a delay for those attempting to intrude, giving the guards time to drive out to meet the intruders.
So in this case the perimeter fence ends some distance on the shore. It ends so as to not allow just walking around its end. Anybody swimming or riding a boat to point beyond that will be seen for long enough by a guard (in this day through security cameras) and someone (either airport security, police or coast guard) will be there to arrest them—or to help them in case they landed or swam there because they had emergency on the sea, which is a good reason to not have a fence there.

Fences, cameras, and guards.  That is often enough to keep trespassers or stow-aways out.
That doesn't mean there is no risk.  I still worry about what terrorists could do to a congested Friday evening line at JFK with speedboats and some RPGs.  That's low hanging fruit, so there must be a plan to mitigate that risk.

How does one "fence" a bay? Could you show an example of an airport, such as Boston's Logan, which "fences" the marine perimeter?


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Why do most military aircraft use different engines than commercial aircraft?
Why do most military aircraft and helicopters use different engine technology (fighters, B52, U2, etc) than most commercial aircraft?
[I removed the use of axial terminology]

Thank you for the comment. However, my question is still why the military prefers to use different engine technologies. And B52's are still using axial flow.

I don't understand the premise of your question. The B-52's JT3Ds were also used on the B707 and DC8 civilian aircraft. Military helicopters use the same turboshaft designs as civilian craft. Other military aircraft use specific turbofans that meet the specifications for their missions just as other civilian aircraft do.

Related: https://aviation.stackexchange.com/questions/17706/how-does-a-supersonic-jet-engine-differ-from-a-subsonic-jet-engine

Two reasons: age and speed.
High bypass turbofans have only been in existence since the 70s - the B-52 was one of the first mass-produced jet powered military aircraft, and turbofans were simply not around at the time. Same for the U-2.
Many fighter aircraft go supersonic, and jet engine thrust T is defined as $T = \dot{m} \cdot (V_e - V_0)$, with $V_0$ the airspeed. Exhaust velocity $V_e$ must be higher than true airspeed in order to generate thrust, and turbojets have a much higher exhaust flux velocity than the cold stream of the turbofan.
Image source
Pure turbojets are noisy and thirsty, and modern fighters use low bypass jet engines with mixed exhaust streams, like the one depicted above. This configuration still allows for the use of afterburners: take-off thrust is where high bypass turbofans are particularly strong.

When military and civilian aircraft of similar speeds are compared, their engines differ mostly by their names. It is simply too expensive to develop a civilian type in parallel to a military type when later both are used in the same way. Examples:

The B-52 engine is called J57 and was made by Pratt & Whitney. The same company called this design JT-3C when it was mounted to the Boeing 707 and the DC-8. Later models used a turbofan development of the J57, the Pratt & Whitney TF33, which was called JT3D in civilian use.
The C-5A Galaxy pioneered large bypass ratio turbofans with the General Electric TF39, which was used on the Boeing 747, DC-10 and A300B as the CF6 later.
Even the same aircraft will sometimes use a different name for basically the same engine, depending on the use: The T-39 Sabreliner used the J60 engine while the civilian Sabreliner called the same engine JT12.

But even when the flight regime is different, component reuse is common between civilian and military engines:

The core of the General Electric F101 (installed in the B-1A bomber, the supersonic first version of the B-1) became the CFM-56 turbofan which is used in the Boeing 737 or the Airbus A320.

Supersonic flight requires a high nozzle velocity, therefore high bypass ratios are unsuitable. However, the differences between sub- and supersonic engines disappear the closer you move towards the gas generator core. High-pressure compressor, combustion chamber and high pressure turbine look and work the same. Civilian engines add a large fan in front while supersonic military engines sometimes add an afterburner. The biggest difference, however, is in the intakes (large pitot intake with blunt lips for subsonic aircraft versus adjustable spike or ramp intakes for supersonic flight) and the nozzle (fixed for subsonic flight versus a complex, adjustable convergent-divergent nozzle for supersonic flight).

I agree with all of the answers posted so far, particularly regarding supersonic speed.  Let me add another perspective: Differences in priorities.
The major factors influencing engine design are: cost, weight, fuel efficiency, and response time (how long from when the pilot moves the throttle to when you have full thrust), and maintainability.  Both military and commercial operators care about all of these, but they differ on which one is most important.
To a commercial operator, fuel efficiency trumps everything else, hands down.  The fuel bill for a large airline can run in the billions of dollars per year, so saving even 0.1% fuel efficiency is worth a lot to them.  That's why you see high bypass turbo fans on all commercial jet liners.  That configuration is the most fuel efficient.  The tradeoff is that once the pilot pushes the throttle, it takes a couple of seconds for that huge fan to spin up. Airlines are willing to live with that in exchange for better fuel efficiency.
The military does care about fuel efficiency, but they also care about response time.  When a fighter pilot wants thrust, he wants thrust right now and the cost is secondary.  Waiting a few seconds for the engine to respond could be the difference between life and death.  That's why you see afterburners on fighter jets.  Afterburners are great at giving you a huge amount of thrust very quickly.  But they are huge gas guzzlers so you would never put them on a commercial jet liner.

“and the cost is secondary” might be, hopefully, “and the cost is the furthest thing from his or her mind.” Someone might care, but the pilot certainly shouldn’t in that situation.

Another reason is noise reduction. Commercial airlines have to deal with noise complaints from people who live near airports.  The military can largely ignore such complaints.  In addition, military bases are often in less populated areas, where there are fewer people to complain.

@KRyan The pilot's mind doesn't matter here. The engineer selected the engines, and he is the someone that cares. (And fuel efficiency matters even if you don't care about cost — more efficiency means less fuel weight, so the aircraft is more responsive. Also, more time on station.)

@fectin The subject of the sentence quoted was “a fighter pilot.”

"so you would never put them on a commercial jet liner" Never say never.

Ok, so almost never ;)

It isn't universally true that military and commercial aircraft use different engines. The military and commercial versions of the Boeing 707/C135 used similar engines as do the military and commercial versions of the DC10.
Combat aircraft however are usually powered by low bypass turbofan engines rather than the high bypass turbofans used in commercial jetliners. The low bypass engines are less fuel efficient but are more compact and have a higher thrust-to-weight ratio than the high bypass engines as well as including an afterburner which can be used to increase thrust at critical periods although at the expense of even greater fuel consumption.
The design of the Lockheed SR71 "Blackbird" reconnaissance aircraft featured turbo-ramjet engines which at high speeds generated most of their thrust in the bypass ducts surrounding the central turbojet engine, using the ramjet principle in which the incoming air is compressed by ram pressure alone without the use of a compressor.
The requirement for supersonic maximum speeds has traditionally been a major factor determining the choice of engines for combat, although such speeds have in practice only been routinely used by reconnaissance aircraft, most notably the SR71. Most manned fighters use so much fuel in afterburner that this capability is rarely used except for takeoff and when manouvering at high g factors, when the extra thrust is needed to counteract drag induced at high angles of attack (AOA). The F22 Raptor however has a "supercruise" capability of achieving supersonic speed without the use of afterburner.

The B-52 and U-2 are not the best examples, both are 60 year-old designs which use 60 year-old engine designs.
The first turbofan flew in 1952, but it took a while for turbofans to become common. In 1961, the B-52H became the first B-52 to have turbofans. By the 1970s, turbofans were used in fighters too.
Modern supersonic fighters use turbofans, for example the F-22 uses the P&W F-119 engine which has a bypass ratio of 0.25. This engine can drive the F-22 at supersonic speeds without using its afterburner.

Another reason why the B52 is a poor example is that the USAF is reconsidering replacing the current TF-33 engines on them with a similar size/performance model currently being used on regional jets to get an ~30% fuel reduction and/or increase in sortie duration.  https://www.defensenews.com/air/2017/02/06/us-air-force-glides-toward-b-52-engine-replacement-plan/

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Can airplane performance be increased by cruising "on step"?
Old timers swear aircraft performance can be increased by getting an aircraft "on step" similar to how boats are operated.

They claimed a couple extra miles per hour (airspeed was in MPH then) were common. The "step" was alleged to be a "just-right" angle of attack which
minimized drag and allowed an airplane to cruise at a higher airspeed than normal on the same power.
Can airplane performance be increased by cruising "on step"?

This has been repeatedly debunked. Here’s one example: https://www.avweb.com/news/airman/184274-1.html

Performance (here: fuel efficiency) cannot be increased over the theoretical optimum. I believe the “on step” terminology simply refers to, out of two possible trim points on the drag curve, picking the faster one - which is hard to attain when operating close to maximum power.

Wouldn't that require to pull the nose into vacuum, which is not possible, since the border is not really firm and the altitude is far too high?

Remember that in the instance of a boat, you are operating on a relatively dense medium below (water) while passing through a relatively less-dense medium above (air), so it makes sense to minimize resistance by making as little contact as necessary with the denser medium (water).  An aircraft is more akin to a submarine than it is to a boat.  A submarine, like an aircraft, is surrounded by a medium of relatively constant density at a given depth/altitude, and there is nothing to "get on top of" so to speak, as there is with a boat operating on the surface.

The Pilot Training Manual For The C-54 Skymaster has this to say about it:

The manual is available at Archive.org

Once you get to Top Of Climb, there are two ways to get the aircraft to the Cruise configuration - the Right Way and the Wrong Way.
The Right Way... set the attitude, wait for the airspeed to reach Cruise Speed, set the power for Cruise Speed, and re-trim during the whole process.
The Wrong Way... set the attitude, set the power for Cruise Speed, wait forever to attain Cruise Speed, and re-trim during the whole process.
If you're using the Wrong Way, then climbing above the Cruise Level and using the subsequent descent to accelerate ("gettting on the step") will appear to work. But it's still Wrong, and it's inefficient.
As with most things in aviation, do it Right first time and every time.

This isn't an answer @RAC, the question is can you increase performance, not how you set cruise configuration. This is more of a comment.

@GdD doesn't the second-to-last paragraph answer that?


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Development Cost?
We all hear about how aircraft development costs multiple billions if not tens of billions of dollars, but what does this money go into?
The material used in making a a single prototype aircraft isn't close to these numbers, neither does the design process cost that much. Custom manufacturing parts for trial also wouldn’t bring up the cost that much.
What do these billions go into? Approval costs? Developing manufacturing plants?

Time being money, the answers here should be highly relevant to this question as well.

That money is spent primarily on engineering, research and development, manufacturing, and flight test. Boeing employs nearly 60,000 people up at their plant in Everett alone, and these people are making at or in excess of $100,000 annually. Then there’s the cost of operating the buildings, the manufacturing and capital required to build the aircraft, cost associated with transportation of raw materials to the manufacturing site.   If new facilities have to be built to manufacture of the aircraft as well as the parts and tooling needed to build it can cost at least 2 to 3 billion.  And that’s just the original equipment manufacturer. There are thousands and thousands of subcontractors on each of those programs providing everything from major components such as engines all the way down to the bolts and rivets that hold the whole thing together.   The costs associated with carrying out a flight test program, as well as numerous small incidentals i.e. rollout ceremony etc.  If you figure an aircraft takes on average about 8 to 10 years from initial concepts to FAA certification, a price tag of around  eight to ten billion dollars in development costs is not unreasonable for a large aircraft.
Complex defense aircraft are equally as expensive. I remember watching a documentary on Northrop's YF-23 airplane, and one of the program managers commented that near the end of the development project on that aircraft, Northrop was spending approximately $1 million a day on that program.

A lot is labor and indirect overhead burden costs (vacation time, sick time, state taxes, federal taxes, 401K matching, oversight of all that). Then engineering - someone has to enter all the thousands of pieces that go into an aircraft and engines. Model it. Create a simulator for it. Develop training for it. Line up business partners across the continent (US and/or Europe for example). Actually make all the pieces. Assemble all the pieces into subcomponents, then major components. Ship all the components to the final assembly site. Connect them all together. Install all the wiring, hydraulics, fuel lines. Test the engine, the avionics, the electrical systems, the hydraulic systems. Eventually test flying and all the costs that go with it. Maybe even paint it.
And I bet I'm not even touching on 1/2 of what goes into it.

certification and flight testing (to partially extend your list)

Developing an aircraft (or really any complex system) is not like someone sketches an aircraft and then some people build it, fly it and then more aircrafts are built.
You start with making concepts, then designs, which are prototyped or simulated. Then these designs are discussed over and over and revised.
And this is not only done for the whole aircraft, but for many components, e.g. fuselage, wings, landing gears, engines, avionics, mission systems, hardware and software.
If and only if all people involved are convinced that this is the most feasible solution in time, quality and cost, the actual manufacturing of the first aircraft takes place. And keep in mind that usually for an aircraft many parts are not just assembled, but also developed from scratch.
And all components are tested alone, then integrated and tested again until the whole aircraft is tested first on ground and then in flight.
So hundreds or thousands of people work for a couple of years for this aircraft while everyone earns 100k, so that's a real big chunk of the money.


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Can or are G-suits ever used for non military applications?
I assume pressure suits are always used by astrounauts or high altitude jet aircraft. The g-suit has a different purpose, design and function. Other than dog fights are there any practical uses for g-suits?

It's G-suit, not g-suite. (Edited question). There's only room enough for one body in a suit.
Yes, counter-pressure suits, aka g-suits, have multiple applications. They are sometimes used medically, in particular for treating internal bleeding, but also a number of less common conditions.
These types of suits are useful in any aircraft that sustain low-pressure or high-g conditions. Most of these happen to be military, but any high-g maneuvering can benefit from the same. Racing pilots in the Red Bull wear them, for instance. Test pilots often do, particularly with high-altitude airplanes.
Another application is spacesuits. G-suits are worn during launches, which except for the Space Shuttle involve high g-loads. As of yet potential is their use for lightweight spacewalking suits.

Thank you for edit of my spelling error.

G-suite sounds like an exiting concept though

I recall that some of the Red Bull air race pilots made use of pneumatic anti-G suits when they flew, but, typically most civilian aerobatic pilots will fly maneuvers of up to +10/-7.5G without the use of anti-G suits.  Reciprocating engine powered aerobatic aircraft cannot maintain sustained high G loading for long before they are exhausted of energy, as opposed to the newer fighters like the F-22, which can sustain a 9G turn until either it runs out of gas, the pilot G-LOCs, or the right inceptor is released.
Civilian pilots flying experimental category surplus military jets in exhibitions (e.g. privately owned F-5s, T-38s, MiGs, etc) will use military issue anti-G suits as part of their flight gear and life support kit.

Salyut space stations had a "negative g-suit" equipment that works exactly the opposite way, e.g. by pulling a vacuum on the legs simulate 1g in a 0g environment.
Chibis vacuum suit

A Soviet *spacesuit introduced in 1978 for cosmonauts about to return from 126 days on the Salyut 6 space station mission. It was a low-pressure suit that forced the body's blood into the legs, an effect similar to that of Earth's gravity. This caused the cardiovascular system, slowed by weightlessness, to work harder and strengthen the heart in preparation for a return to gravity. Similar units were worn regularly by crews on the ... ...

Also there are other leg compression equipment for sustained standing and walking (1g for a long time is also a problem) e.g. compression socks and compression leggings. I think this one fits the question best because it is truly an anti-g equipment.

Also there are IPC (Intermittent Pneumatic Compression) devices

Intermittent pneumatic compression (IPC) devices are inflatable
sleeves that prevent blood clots. You wear them on your calves (lower
legs) to help your blood circulate. A plastic sleeve slides over and
past each foot. Then, it goes around each calf and plugs into a small
machine that makes it inflate.

image source: amazon.com

Very interesting. I never thought of compression stockings something I  have to use myself everyday for edema. Uses the same concept Thank you for interesting research

Similar pneumatic compress leggings are often used after surgery. I know I had them for a couple of days after abdominal surgery. They are suppose to prevent blood clots in the legs  I think they also make them for shoulders and arms.


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Can a misfired BrahMos missile be aborted?

Errant Indian Missile Nearly Led to Pakistan Retaliatory Strike

Could the missile have been stopped before it hit the ground?
Specific parts to the question:

Does the BrahMos missile command and control center have the capability to steer the missile if they realize that the missile has been misfired? Or, is it fire & forget?

Does the BrahMos missile have a "self-destruct" option?

Can retargeting or self-destruct be deployed before the missile hits the ground in 3 minutes?

The answer to what I presume was your real question - "Could the missile have been stopped before it hit the ground?" - is "No". In detail on the subquestions:

Likely. The Brahmos missile is loosely based on (more like "inspired by") the Granit missile that does have an onboard datalink for target selection. There's no confirmation that Brahmos has the same, but it's reported to be a very sophisticated missile, so it's probable.

However, the launch platform is unlikely to have the ability to use this datalink. It's possible for a combat aircraft - altitude gives comm range, and aircraft are under the singular authority of their crews, so they may be able to do this in time. It's somewhat possible for a ship, while there is a line of sight.
Ground launchers cannot communicate with missiles once they have been fired. This is, if nothing else, due to the horizon effect. Ground launchers are also less sophisticated in general.
Such communications are encrypted. The encryption keys are generated and exchanged at missile boot-up (in modern documented military encryption protocols). If the missile misfired, it doesn't have a datalink established, so no one is able to communicate with it.

Very likely yes, most such missiles do have a self-destruct capability.

The first Brahmos entered service in 2005 (in many ways, it was ready in 2002), but it's been an ongoing development and modernization project for at least a decade since. Specifically the flight control system and software were modernized and refined in India.
Another Indian missile, tested in 2013, was self-destructed, indicating that India does like this feature in their missiles. Self-destruct is a software feature, so, even if the original missile didn't have it, India had the opportunity to add it in the modernization process.
As with retargeting, communicating with the missile may not be possible, especially from the ground. Again, it would only be possible with a properly initiated launch, not a misfire. Self-destruct implies an encrypted link - you don't want the enemy to be able to just turn your missile off.

No. Not realistically.

It's possible if you expect the missile to potentially veer off course, and are actively monitoring for that event, and are trained and pre-authorized to take that action.
This high readiness happens when you're test-firing a missile.
For a missile that has been accidentally fired on the ground during maintenance, as reported, the answer is a resounding no.
First, the maintenance crew has no authority over the missile and its target selection or self-destruct (if present). They also don't have enough time to figure out what's going on, who has the authority, how to contact them directly, what exactly to communicate, and so on. It's going to go up and down the chain of command.
Second, the fire control module isn't in the TEL (transporter-erector-launcher) truck. The land-based Brahmos missile uses a separate command post vehicle.
If the missile truly misfired, rather than was fired by mistake, that means the issue most likely occurred within the missile or the TEL. The command post in this case most likely wouldn't even be online.
Third, a misfired missile might not have all of its own computers properly started and set up. If it's just the engine that started, there's nothing to control the missile. Since Brahmos is supersonic, it must've had a working flight control system, but many other systems could still be offline or improperly initialized.
P.S. Related: How can a supersonic cruise missile be intercepted?
Anti-ship missiles are built to deal with attempts to shoot them down. So the design principle is "fail-deadly". If radar and comms are destroyed, the missile will try to hit its last target point. A misfire without proper target input is likely to be treated the same way as combat damage.

It's worth noting that the Nirbhay is a newer generation of missiles. which wasn't even operational in 2013, when that article was written; those were qualification tests. So assuming the older BrahMos has the same capabilities is not 100%. It's not clear to me why you think BrahMos "uses Indian avionics". The BrahMos is a pretty close derivative of the P-800 Oniks, at least form the outside.

Your other points on them not having enough time to react even if they had the capability is entirely reasonable though. It looks like the whole event took like 7 minutes, and the missile veered towards Pakistan after a couple of minutes, so that would have made decisions even more complicated.  Also, cruise missiles do have the ability to load pre-plotted courses that contain pre-planned route changes, so some kind of pure software / data-load error can't be ruled out.

Unfortunately, I haven't see altitude changes on that course. The P-800 normally has a lo-hi-lo attack profile (it's a tradeoff with range on supersonic missiles like the BrahMos), which would have made tracking mid-course easier, but if it was staying low for some reason (error or pre-planned data) that would have made tracking it hard even for the Indians. Actually, it [looks[(https://thebulletin.org/2022/03/not-much-happened-after-indias-accidental-cruise-missile-launch-into-pakistan-this-time/) like it reached 40,000 feet in altitude, which suggests that they could track it.

OTOH, even though they have a deconfliction line, neither side called (same source) which makes some think the event happened too fast for either side's command and control to make much in the way of decisions.

But this was not fired from a normal test range, so the usual tracking capabilities for that kind of event were probably not deployed in the area.

@Fizz BrahMos was a Russian-Indian collaboration, with Russia providing the initial expertise, but India's IT industry played a major role in developing the flight control system as well as launch control. The guidance hardware is Russian, but the software was modernized by India.

@Fizz Regarding the Nirbhay, while it's newer chronologically, it's an indigenous Indian development, and the timeframe is so close that it overlaps with Brahmos. For a software comparison, if you write a new OS, it's going to either be based on Linux, or have fewer features than a decade-old Linux distro. These things take time, and the Brahmos project was a major enabler for India's own R&D.


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Are there any GA trainer aircraft without toe brakes?
I'm a student pilot, and I've built about 20 hours on a Cessna 172. I also have an old ankle injury that makes it hard to bend my left ankle, and I'll probably be getting an ankle fusion later this year. I know I won't be able to work the left brake with a fused ankle. Are there any good options for trainer aircraft with other kinds of brakes?

Can you use heel brakes? Or are you looking for hand brakes only?

Would heel brakes float your boat? Consider a Taylorcraft.

I'd be willing to try heel brakes. Just need to find a flight school near me that would rent a plane with one.

There are still many Ercoupes in the fleet that don't even have rudder pedals, never mind toe-brakes on the rudder pedals.
You may also want to consider arranging for a more commonly-available trainer (e.g. Cessna 152, Piper Tomahawk, Diamond DA20, etc.) to be equipped with hand-controls for braking. This is done for individuals who have any number of reasons that they can't operate the rudder pedals with their feet, such as paraplegia, deformity, etc.
See e.g. https://www.freedomintheair.org/hand-controls/, https://www.newmobility.com/2019/01/pilots-planes-hand-controls/, https://www.wired.com/2009/08/hand-control-airplanes/, https://abilitymagazine.com/hand-controls-for-flying/, etc.

Russian/Soviet GA trainers Yak-18T and Yak-52 have a manual brake handle on the yoke/stick. The latter is quite common in the US, but being an aerobatic airplane, it may not be very suitable for your experience.
The Australian Jabiru light GA aircraft have a brake handle on the central post between the pilots.

The 1964 Piper Cherokee that I rent has inoperative toe brakes. In order to stop the aircraft after landing, you have to slow down past the maximum taxiing speed using aerodynamic braking. Then, you use the parking handbrake to come to a complete stop.
I have never had to make an actual soft or short field landing with this aircraft. But, it would be challenging. Personally, I would avoid it. It might be even harder in a Cessna 172. I have not flown one with a handbrake as responsive as that Cherokee.

YIKES!  Surprised that's even legal. What's the plan for an aborted takeoff?

@RalphJ - Well, the plane does not have an MEL or even an MMEL that I know of. Plus, the brakes still work. And, they are pretty responsive with plenty of feel. There is just no differential braking.

From what I've read, toe brakes on Cherokees were optional before the 1980s. According to page 7 of the POH, "The brakes are actuated by a hand lever and master cylinder, which is located below and behind the left center of the instrument sub-panel."
http://houltonflyingclub.com/wp-content/uploads/2017/04/Cherokee-140-Owner_s-Handbook.pdf

"the plane does not have an MEL" -- I don't think that's how it works. The MEL offers a more permissive way to deal with inoperative equipment, as I understand it. Lacking one, the airplane is unairworthy if any of the equipment required for certification is not operating as certified. One could get a ferry permit from the FSDO so that the airplane could be flown for repairs, but I doubt it's legal to operate on a regular basis with brakes that are inoperative.

@PeterDuniho - I guess that would really depend on the airworthiness certificate and original type certification data sheet. After all, it would be perfectly legal to fly day VFR with an inoperative DG, Attitude Indicator, or even radios as long as they are placarded INOP or removed, and notations are made in the aircraft’s logbooks. If it were unairworthy, I would think that the A&P would have to pull the aircraft out of service. In this case, the aircraft continues to get its Annual, 100-hour, and ADs cleared and up to date.


text:
Does EASA allow IFR, NVFR or SVFR in gliders?
Is it legally possible in Europe to get clearances for IFR, night VFR or special VFR while flying gliders? Specifically, I'm interested in sailplanes, powered sailplanes and ultralight sailplanes (MTOW below 472.5kg).

I don't think IFR is possible. It requires maintaining assigned altitudes. Remaining along a specific route and crossing fixes at assigned times. A glider is also unable to do a holding pattern at an assigned altitude. A IFR aircraft is also required to change altitude at minimum ROC as assigned.

It's not possible to get IR for any of those. I think EASA now has flying in clouds rating for gliders. For night flying you will need a glider that is certified to do that. I don't know any manufacturers of night gliders. Blaniks had an option to fly at night but most of them cannot fly now at all.
SVFR may be possible in theory but it will be crazy. Maybe you can be towed in special VFR but this will be dangerous. It also depends on whether the country in which you are flying allows SVFR.


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What are these beams sticking out of the Su-17's nose?

As visible in the image above, there are these 2 beams sticking out of the Su-17's nose. One is longer and one is shorter.
What are the purpose of these beams and exactly what do they do?

Air speed sensor and aoa sensor

conical nose reminded of its predecessor as much as the MiG-21, and ended with two long poles, one of which contained the very classic Pitot tube and the second a fire control calculator.

Source :https://www.avionslegendaires.net/avion-militaire/sukhoi-su-17-20-22-fitter/

Two protuberances extended the nose: a Pitot tube and above all a pole supplying measurements to an ASP-5ND fire control system

Source:https://aviationsmilitaires.net/v3/kb/aircraft/show/2208/sukhoi-su-17-otan-fitter

Those are Pitot tubes, used to measure the dynamic pressure in front of the aircraft, from which the airspeed can be calculated.
Here you can see them covered while on the ground to prevent contamination:

And here is a similar system on another aircraft from the same manufacturer, the Su-25:

Those are pitot tubes, used for measuring airspeed. Two pitot tubes were used for backup purposes in case one forms ice or blocks for any reason (A380 has three). This tube configuration was introduced in Su-17M after moving them from right to the left.
An extract from source -

The Su-17M also featured a number of rearrangements and tweaks. One
  distinctive change was to move the backup pitot tube to above the left
  side of the engine intake, giving the aircraft a "double-pronged"
  appearance. The positioning of the backup probe on the right side of
  the nose had led to minor problems with stall characteristics. The
  parachute fairing at the base of the tail was changed to a more
  streamlined configuration that accommodated a single cruciform
  parachute, while the antenna for the Sirena system was relocated from
  the tailtip to just above the parachute fairing. The hydraulic system
  of the aircraft was completely redesigned, with a dual instead of
  triple system.

I'm not sure why one is shorter than the other though.


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What is the ceiling altitude for the Airbus A320?
About a week ago, I was flying from Boston to San Juan in an A320 and noticed that the flight was staying at about 42000 feet for the major part of the trip, according to the flight map screen on the plane's entertainment system. That struck me as an unusually high altitude and I am even more surprised now that I have read a little on the subject. I am wondering if that was even possible, or the altitude readout to the entertainment system was simply wrong. The flight proceeded uneventfully in other ways, and was on time.
What is the ceiling altitude for the Airbus A320?

According to wikipedia the service ceiling for A320 is 39,000 ft (the A319 and A321 have a service ceiling of 41,000 ft).

Do you remember the flight number and exact date?

From a legal standpoint in the US: Flying above 40,000 ft requires special certification, but is not impossible for a civilian aircraft (many business jets fly well above). This is because in case of depressurization the aircraft must go down to 15,000 or 10,000 ft to find safe breathable air and this takes time, but hypoxia can create permanent brain damages or be lethal in a few seconds. See US 14 CFR 25.841. At a previous time the ceiling was 41,000 ft.

Was this pressure altitude or geometrical height? The certified service ceiling is based on pressure altitude, the geometrical height may be higher, especially in high pressure area's and warm weather conditions.

@DeltaLima The certified service ceiling is based on density altitude not pressure altitude. https://en.wikipedia.org/wiki/Ceiling_(aeronautics)

Related: http://aviation.stackexchange.com/questions/11393/is-there-a-legal-maximum-altitude

I have just found the flight stats for my flight -- it departed minutes into April 16, so I was not seeing it listed for April 15th. I am sorry, this probably was a non-issue from the start. The altitude is listed at more or less steady 36000 feet throughout.. Also, I just noticed that the LATITUDE reading is in the vicinity of 42... "latitude" vs "altitude" -- could be easily confused (just guessing). In any case, it seems as though my impression of the altitude was not correct. Thank you for all the answers.

@mins The Part 25.841 pressurized limit is now effectively 43,000 ft by certification waivers. The A380, A350, and 787 are all certified to 43,000 ft.

This question is a bit more generic. Ceiling altitude depends on many things such as (environmental conditions, engines operative, a/c aerodynamic characteristics, e.t.c), each factor by itself and in combination, can affect the ceiling altitude. You can get an idea and some definition from here: https://en.wikipedia.org/wiki/Ceiling_(aeronautics) .

For most of the A319/A320/A321 aircrafts Maximum Certified
  Altitude according to FCOM is FL391 considering (2 engines operative
  and environmental allowing.)

Now according to FCOM DSC-22_20-50-10-28, (controls and indications) you can find the MCDU page,
REC MAX:
This field displays the recommended maximum altitude (in magenta), that is computed based on the current gross weight and temperature, and assuming that the anti-ice is off (Refer to QRH graphs, if icing conditions are expected). It provides the aircraft with a 0.3 g buffet margin, a minimum rate of climb at MAX CL thrust, and level flight at MAX CRZ thrust. This field is limited to FL 398.
If one engine is out, this field displays the recommended maximum engine-out altitude, that is computed based on the long-range cruise speed and assuming that anti-ice is off.

Note: The OPT or REC MAX field may display a value up to
FL 398. However, the current aircraft’s maximum certified altitude is 39 100 ft. Disregard the OPT or REC MAX value, if it exceeds FL 391.
Now for entertainment system, (again according to the books), reads and display data taken from the FMGC.
One scenario is the input from the pilots, in MCDU was the displayed LVL, and subsequently in the entertainment system, the displayed LVL
was that (after the CRUISE phase), even though the actual altitude was
different that the displayed.But again it's impossible to insert an altitude above the value of "FL398" MCDU says "ENTRY OUT OF RANGE".

So the conclusion As kevin said already, possibly wrong data were
displayed.

Hello Lidakis Emmanuel, welcome to Aviation.SE!

Let us state the known facts (from the question and its comments):

The altitude reported on the passenger entertainment system was observed to be 42,000 feet.
The aircraft was an Airbus A320.
Looking up the flight history shows the plane flown at 36,000 feet.

Case #1: aircraft was flying at FL420
As noted in the comments, this is beyond the certified service ceiling of the A320. Also, this would contradict (3), which data is collected via ADS-B and presumably correct.
Case #2: the OP misread "latitude" as "altitude"
From my experience flying as a passenger, the raw longitude and latitude data is not displayed on the passenger's flight information screen. There would be no need to, since (most) passengers would not carry a map with them and plot the coordinates onto it. The coordinates themselves are therefore useless information, and I doubt the engineers who designed the software of the entertainment system would put it in.
Case #3: reported altitude was geometric height
I don't have a source for this, but I don't think the passenger's entertainment system would have a function to convert pressure altitude into geometric height, when even the pilots don't have it.
Case #4: the reported altitude does not correspond to the altimeter's reading
The flight information display reports data captured in the cockpit in real time. Data such as the plane's location, speed, altitude, vertical speed, heading and winds aloft, are supplied by the flight management computer and are identical to those seen by pilots. I know this is the case as I always watch the flight information screen closely during takeoffs and landings, and the readings correspond to how a pilot would have flown a SID or STAR. (I always fear the pilots may mess up and I would feel safer if I'm in the cockpit, but since I'm not allowed to do that, I watch the flight information screen to act as "passenger monitoring".)
I'm left with one conclusion:
The altimeter's reading was wrong. There are multiple altimeters on an airplane like this. If one of them malfunctions, the pilots can set the source of the autopilot and flight management computer to another good altimeter. But since the passenger's flight information display is a non-critical system, its source probably cannot be switched, hence the wrong data is displayed in the cabin (most passengers don't know what are the nominal values anyway).

Ad case #3: It is plausible and likely. The pilots have no use for geometric altitude, so it is not provided to them, but it is readily available from GPS and used at least by EGPWS. So IFE system should have no trouble getting it. And it is likely to use it, because it is what laymen expect.

That said, having pressure altitude 36000 correspond to geometric altitude 42000 would require very high pressure or very high temperature.

Thank you very much for looking at the problem from all possible angles. I agree that your Case #4 is the only plausible explanation, conspiracy theories aside. The altimeter feeding data to the entertainment screens must have been flawed. Flying the same route home, I was observing a steady 36000 feet reading.

Case #3 seems unlikely. The question says the altitude was 42,000ft for "a major part of the trip" and, while Boston is indeed at about 42deg north, San Juan, Puerto Rico (the only San Juan that currently has flights to Boston, and these are by JetBlue, which flies Airbuses) is at 18deg north, due SSE of Boston. On the other hand, some passenger flight information displays do give the latitude and longitude, contrary to your suggestion that they wouldn't. I've often noted down the co-ordinates when taking photographs through the window.

Nobody ever flies at FL420, ever. RVSM airspace, where usable altitudes are 1000' (10 FL's) apart, stops at FL410. Above that, only "odd" altitudes are used: FL430, FL450, FL470. Between the lower service ceiling & the unusability of FL420, I'd totally agree that the entertainment system's altitude readout was wrong. What causes this, however, is a harder question; if the aircraft altimetry systems were messed up, getting an ATC clearance into RVSM airspace (above FL280) could be problematic at best.
I'd wonder if the entertainment system wasn't jumbling things around somehow & putting bad data on the displays. And then that glitch was fixed in the "return home" airplane.
(Side note - @JanHudec makes 2 excellent point in comments on the other answer about the possibility of the IFE using GPS altitude. Other then the magnitude of the 6000' delta between the flown altitude and the reported altitude, I could readily believe that the IFE might be reporting GPS altitude rather than the more accurate info from the FMS.)

It has just come to mind that the altitude reading on the entertainment screen that one typically sees in flight is usually remarkably steady and looks, maybe, like a rounded number(?). I am wondering if the airplane is actually staying rock steady at exactly FL370, for example, or the readout is "stabilized" and rounded off before it reaches the entertainment screen. If that were the case, the "math" of that process could have been the culprit. I wonder if the pilots see a more dynamic digital real time altitude readout in the cockpit.

I need to look up to verify this, but if the plane has 3 static ports (which is a reasonable assumption), having one of them inoperable may not ground the plane or keep it out of RVSM according to the MEL (minimum equipment list), as long as the pilots are aware of it and adjusts the source correctly.

I've been cleared FL410B430 so it isn't strictly correct to say that no one ever flies at FL420.  In this case, however, they certainly weren't.